UV based water purifiers

[Lou_tribal]

Hello fellow TFers,
I am looking at improving my plumbing setup to get more potable water capacity, from saving it to making it.
First I have not enough space to put a water maker with its own engine etc.
Second I am only in fresh water for at least a couple of years so no need for desalinization.
I was looking at some filtration/purification systems, based on 3 stages filtration to remove sediments, color/odor, chemicals and finally purification based on UV lamp. Looks like the setup is quite energy effective and could easily run from my small genset or even from a small inverter.
I see it as a way to fill up my tanks when needed not for continuous water supply.
Does anybody have this aboard r any experience with these?

L.

 

[FF]

We have used a UV setup in our RV.

I hooked to to see the water both on filling the tank , and again when using the water.

The light must be on for a few seconds to get the water in the unit , so I do not know how well it worked doing tank water .

.Next time I would clear the water going into the accumulator tank (10G) rather than the sink.

Worked well no visits from Montezuma.

 

[twistedtree]

Hello fellow TFers,
I am looking at improving my plumbing setup to get more potable water capacity, from saving it to making it.
First I have not enough space to put a water maker with its own engine etc.
Second I am only in fresh water for at least a couple of years so no need for desalinization.
I was looking at some filtration/purification systems, based on 3 stages filtration to remove sediments, color/odor, chemicals and finally purification based on UV lamp. Looks like the setup is quite energy effective and could easily run from my small genset or even from a small inverter.
I see it as a way to fill up my tanks when needed not for continuous water supply.
Does anybody have this aboard r any experience with these?

L.

The UV treatment things are pretty commonly installed on larger Nordhavns and people speak highly of them. In preparation for traveling to Mexico, I am assembling one now with intentions to use it exactly as you describe.

Most Nordhavn's have them set up to treat all water as it is drawn out of the tank for use. That means the UV lamp runs all the time and I'm a stickler for power consumption so don't like that. Plus, I'd rather keep contamination out of my tank in the first place. So I am taking the same approach as you and filtering/treating as the water goes into the tank rather than as it is draw out.

The set up is pretty straight forward. There is a big blue 4"x10" filter canister, followed by the UV purifier. I plan to use a charcoal filter that will extract particulates, plus chemicals. Then the UV will kill any micro beasties. It connects inline with the dock hose. There is also a flow regulator to ensure the fill rate doesn't exceed the treatment rate of the UV purifier. The water needs to spend a certain amount of time exposed to the UV to kill the beasties, and if the water is flowing too fast, it doesn't get enough exposure.

There is only one problem.... I haven't tried it yet. And like fuel treatment, oil additives, and lots of other magic elixirs, performance of these things is an exercise in proving a negative, which is of course impossible to do. So there is a certain leap of faith.

 

[Lou_tribal]

The UV treatment things are pretty commonly installed on larger Nordhavns and people speak highly of them. In preparation for traveling to Mexico, I am assembling one now with intentions to use it exactly as you describe.

Most Nordhavn's have them set up to treat all water as it is drawn out of the tank for use. That means the UV lamp runs all the time and I'm a stickler for power consumption so don't like that. Plus, I'd rather keep contamination out of my tank in the first place. So I am taking the same approach as you and filtering/treating as the water goes into the tank rather than as it is draw out.

The set up is pretty straight forward. There is a big blue 4"x10" filter canister, followed by the UV purifier. I plan to use a charcoal filter that will extract particulates, plus chemicals. Then the UV will kill any micro beasties. It connects inline with the dock hose. There is also a flow regulator to ensure the fill rate doesn't exceed the treatment rate of the UV purifier. The water needs to spend a certain amount of time exposed to the UV to kill the beasties, and if the water is flowing too fast, it doesn't get enough exposure.

There is only one problem.... I haven't tried it yet. And like fuel treatment, oil additives, and lots of other magic elixirs, performance of these things is an exercise in proving a negative, which is of course impossible to do. So there is a certain leap of faith.

I did some homework and looks like companies selling these UV systems recommend not to put it before storage tank without much more details. I understand it in the way that water in the tank, even if coming pure into it, can be contaminated afterward (by biological/dirt from the tank itself).
However I guess this can be mitigated by keeping the tanks clean, renewing water often and use of chlorine.
What I imagine doing is having the UV system before the tank to create purified water, than use controlled dose of chlorine in the tank to keep it clean, and use 3 stages filtration after the tank to keep water pure and remove chlorine residue when using the water.
Like you I do not want to use the UV for water out of the tank as it would draw energy what I try to avoid as much as possible.

I checked and each UV reactor has a flow rate for optimal use of UV dose.
As my tanks are relatively small (2 x 35 gal) I would use a relatively small system too. With one of the smallest I saw, at optimal flow rate it would take me less than half an hour to refill both tanks which is just perfect.

May I ask what system will you use?

L.

 

[twistedtree]

I did some homework and looks like companies selling these UV systems recommend not to put it before storage tank without much more details. I understand it in the way that water in the tank, even if coming pure into it, can be contaminated afterward (by biological/dirt from the tank itself).
However I guess this can be mitigated by keeping the tanks clean, renewing water often and use of chlorine.
What I imagine doing is having the UV system before the tank to create purified water, than use controlled dose of chlorine in the tank to keep it clean, and use 3 stages filtration after the tank to keep water pure and remove chlorine residue when using the water.
Like you I do not want to use the UV for water out of the tank as it would draw energy what I try to avoid as much as possible.

I checked and each UV reactor has a flow rate for optimal use of UV dose.
As my tanks are relatively small (2 x 35 gal) I would use a relatively small system too. With one of the smallest I saw, at optimal flow rate it would take me less than half an hour to refill both tanks which is just perfect.

May I ask what system will you use?

L.

Ours is a Viqua VH410. I sized it for the quickest hose fill that seemed reasonable, and it ended up at 18GPM which is probably bigger than needed. But our tank is 600 gal so there is motivation to fill as fast as possible, and in a few places we have found very fast fill rates. I don't recall the details, but I think the next size down was a bit slower than I wanted, so I went for the next size up and ended up with this one.

Cost for the UV device and the Big Boy filter canister was about $700. I bought from FreshWaterSystems.com, having used them for other purchases and been satisfied.

As for placing the UV before or after the tank, I think the point is that some degree of chlorine in your tank, at least some of the time, is important to keep the tank and plumbing sterilized. Accomplishing that really depends on how you operate.

We take on dock water in the US and Canada on a semi-regular basis. We do not pre-filter with charcoal, so get our dose of chlorine with each fill.

In between dock water fills, all water comes from the water maker, and typically makes up 80-90% or more of our water consumption. That water is obviously not chlorinated.

So far we have not taken on dock water that is untreated, but will be able to do so with the UV purifier. That water going into the tank will be just like water maker water, i.e. filtered but unchlorinated.

If we go long enough without any chlorinated dock water to freshen up the disinfecting of our tank, we can always dose it manually. My wife
tracked down stuff called Puragene that she favors over chlorine.

 

[Lou_tribal]

I checked Viqua systems and the smallest of their system would be perfect for us. It would allow to fill our tanks in 15 minutes at the optimal UV dose.
Like you wrote, keeping your tank clean and well maintained is the key and does not require much effort.

Thank you very much for your input.

L.

 

[Lepke]

Ebay or Amazon are two of the less expensive places to buy a UV lamp. Also filter sets. If you're doing lots of water, by Big Blue 4.5 x 20. They last many times longer than the small ones. The UV light needs to be rated to the maximum flow going thru. At least 6 gallons a minute. Higher flows, longer lamp/tubes. The key to sterilization is the time the water is exposed to the UV rays, hence the gpm rating.
I have mine after the watermaker, but before the tank. I also add chlorine to the tank when making water and take chlorine out with post tank filters. Because the tanks will always get organisms, no matter how clean or sterile the water is going in.
If you're doing river water, buy some washable 20 and 5 filters to run before before any small micron filter. I use a 1 micron, then a CTO and GAC after the tanks. They take out chlorine and many organic compounds, pesticides, and other nasty things found in tap water, let alone river or lake water. The carbon filters also make the water better tasting. When making fresh water out of existing fresh, I still run it thru the RO membranes, but at reduced pressure.

 

[Wxx3]

The reason they specify to put the UV killer after the tank and just before you use the water is because nothing is 100%.
So the idea is that if you are left with water let's say at 5 parts per billion (I made these numbers up), it's safe to drink.
But if it then is stored in a tank, those 5 parts will multiply quickly, thus rendering your water unsafe.

Why buy an expensive system and then re-engineer it?
ANd if you are using Chlorine anyway, why go to some much trouble?

Two rubbers don't make you twice as safe.

 

[Lou_tribal]

Richard, I am looking at being able to increase my water autonomy by making water from raw source (read river and lake). Looks like filtration followed by UV would be the best way to achieve this.

L.

 

[twistedtree]

The reason they specify to put the UV killer after the tank and just before you use the water is because nothing is 100%.
So the idea is that if you are left with water let's say at 5 parts per billion (I made these numbers up), it's safe to drink.
But if it then is stored in a tank, those 5 parts will multiply quickly, thus rendering your water unsafe.

Why buy an expensive system and then re-engineer it?
ANd if you are using Chlorine anyway, why go to some much trouble?

Two rubbers don't make you twice as safe.

The post-tank locations of the UV purifier is probably the most common, and I can't deny that it's the "100%" location. But that 100% comes at the cost of running the UV light all the time. I suppose you could rig up some sort of flow sensing and switch on the light only when there is water flow, but I think they call for some minimum on time before sterilization begins. I haven't though that part through, but all the post-tank UV systems I've seen run all the time.

For me, I'm willing to take that little extra risk to not have the UV light running all the time. The gamble is that I'll get enough chlorine through my system, often enough, to not grow a biological weapon in my tank. Will I continue to win that bet? I hope so, but there is no guarantee.

 

[Chrisjs]

Not sure bout this but I think the issue with UV location is related to flow rate. UV does not kill "instantly". There needs to be some exposure over time. I think the reason the UV is positioned at the tank draw is because the flow rat there is significantly less than the fill rate from a dock hose. Consequently, the exposure time is longer. Another (better) option/addition to UV alone is to add an ultrafiltration step that will remove bacteria and viruses. This is finer than an RO membrane, and would require a dedicated high pressure pump.

 

[twistedtree]

Not sure bout this but I think the issue with UV location is related to flow rate. UV does not kill "instantly". There needs to be some exposure over time. I think the reason the UV is positioned at the tank draw is because the flow rat there is significantly less than the fill rate from a dock hose. Consequently, the exposure time is longer. Another (better) option/addition to UV alone is to add an ultrafiltration step that will remove bacteria and viruses. This is finer than an RO membrane, and would require a dedicated high pressure pump.

You are correct about the whole exposure time thing, and it is why various UV purifiers have maximum flow rates. As a result, whether installed on the fill side or the consumption side, you need to ensure the flow rate remains below the UV devices rated flow to get the desired purification.

To ensure the flow rate is acceptable, you can simply size things so the probability of excessive flow is low to zero. The other approach is to install a flow limiter that will ensure the flow rate doesn't exceed a pre-determined level even if there is a call for more water. I took the later approach for exactly the reasons you mention. There is a lot of variability is dock hose pressure and flow rates, and the flow limiter seemed like the best way to ensure the flow is never too fast for the UV to do it's job.

 

[Chrisjs]

I agree with your recommendations but wonder how many people really want to take even longer to fill their water tanks, especially while cruising and filling water tanks up at fuel dock.

 

[Lou_tribal]

I agree with your recommendations but wonder how many people really want to take even longer to fill their water tanks, especially while cruising and filling water tanks up at fuel dock.

But it is not the issue I try to solve here. As mentioned what I want to achieve is pumping water from the river purify it and store it. The flow rate of the smallest system I found is 5 gal/min, approx the flow of a water saving shower. At this rate it would take me 15 minutes to fill up my tanks which very reasonable.

L.

 

[Chrisjs]

I woul not drink river water anywhere around here or anywhere I have cruised on the East Coast. They are certainly not pure mountain streams

 

[Lou_tribal]

Indeed so the need for filtration and purification 3 to 5 stages filtration is supposed to remove most of contaminants ( sédiments, chemicals, tanins etc) and UV are supposed to kill any residual life forms.

Maybe I am too much optimistic but that is the way cities are making water, and water is coming from the same source.


L.

 

[Wxx3]

You are correct about the whole exposure time thing, and it is why various UV purifiers have maximum flow rates. As a result, whether installed on the fill side or the consumption side, you need to ensure the flow rate remains below the UV devices rated flow to get the desired purification.

To ensure the flow rate is acceptable, you can simply size things so the probability of excessive flow is low to zero. The other approach is to install a flow limiter that will ensure the flow rate doesn't exceed a pre-determined level even if there is a call for more water. I took the later approach for exactly the reasons you mention. There is a lot of variability is dock hose pressure and flow rates, and the flow limiter seemed like the best way to ensure the flow is never too fast for the UV to do it's job.

Yes, exposure time is critical to the UV system. BUT that's not what I am referring to.
I'm referring to the specification that the UV filter should be on the end use side of the system, not at the fill tank side, no matter what the rate is.

It's an issue of the amount of bacteria still alive AFTER the UV treatment.

The idea is that some bacteria is still alive, but in such small concentrations that they do no harm. HOWEVER if stored, the bacteria will rapidly multiply, leaving the water unsafe again.

If your intention is to put Chlorine in the tank in any case, there is absolutely no point in giving it a UV treatment at all.